The present invention is related to a method for discriminating optical disks from each other in an optical disk apparatus.
In optical disks, there are various sorts of media such as BDs (Blu-ray disks), DVDs, and CDs. While there are a large number of optical disk apparatus adaptable to a plurality of media, these optical disk apparatus are required to discriminate the sorts of inserted optical disks from each other. In BDs, influences caused by spherical aberration are large, and it is difficult to discriminate BDs from each other unless spherical aberration is corrected to a predetermined level by a spherical aberration correcting element. JP-A-2004-311004 discloses a method for performing the discrimination of media from a medium whose numerical aperture is low in order to prevent collision, and describes that spherical aberration is corrected in combination with the numerical aperture at this time. JP-A-2006-344268 discloses a method for discriminating the total layer number of information recording planes of a medium by performing a sweep process in which an objective lens is driven two or more times by changing a correction amount of spherical aberration.